Gintautas Abrasonis, Klaus Morawetz
Ion irradiation during film growth has a strong impact on structural properties. By means of linear stability analysis we demonstrate that ion irradiation of growing binary alloys leads to the formation of composition-modulated surface patterns. We show that the ion-to-atom arrival ratio $R$ is the pattern control parameter. Close to the instability threshold we identify different regimes of instabilities driven by ion-induced surface roughness processes or roughness-composition feedback interactions. In particular, the synergistic effects of the curvature-dependent displacement coupling to the preferential sputtering or to the diffusivity are found to induce instabilities and pattern formation. Depending on the film growth and ion-irradiation conditions the instabilities show stationary or oscillating behavior. The corresponding phase diagrams are presented in terms of experimentally accessible parameters. This presents opportunities to control surface patterning and to grow three-dimensional laterally or vertically ordered nanostructures.
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http://arxiv.org/abs/1109.5461
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